Crosslinked protein-based separation membrane and application thereof

ABSTRACT

A crosslinked protein-based separation membrane and application thereof. The separation membrane is formed by attaching a crosslinked protein nanomembrane to a porous membrane, the crosslinked protein nanomembrane is formed by crosslinking a two-dimensional nanomembrane which is formed by phase transition of a protein with a crosslinking agent, the separation membrane contains a dense surface layer and a support layer, the dense surface layer is the crosslinked protein nanomembrane, and the support layer is the porous membrane; the protein is any one of lysozyme, bovine serum albumin, insulin, and α-lactalbumin; the crosslinked protein-based separation membrane has a good biocompability, may serve as a dialysis membrane for blood purification, and has a higher retention ratio for large molecular proteins.

TECHNICAL FIELD

The present invention relates to a separation membrane, andspecifically, to a green and mild separation membrane with easypreparation and a controllable pore size, and uses of the separationmembrane.

BACKGROUND

Due to the characteristics such as high separation efficiency, nosecondary pollution, and easy operation, the membrane separationtechnology has been widely applied to petrochemical engineering, sewagetreatment, medicine and health, food processing, and other fieldscurrently. The membrane material is one of the essentials of themembrane separation technology. At present, the common membranematerials mainly include organically synthetic polymers. However, thepreparation method of polymer membranes is complex; and generally,organic substances (such as, protein, colloid and microorganism) areeasily adsorbed in a feed solution during separation; the proteinnonspecific adsorption on the surface of a membrane further causesnegative effects, such as blood coagulation while being in contact withblood, resulting in reducing the flux and selection of the separationmembrane. Hemodialysis treatment is one of the common treatment means totreat uremia patients. The purpose of the blood purification membrane isto achieve exchange of substances mainly through diffusion/convectionprinciples, thus cleaning up metabolic wastes and excessive moisture,and maintaining electrolyte in the body. However, medium to largemolecular toxins cannot be cleaned up by a conventional hemodialysismembrane. Therefore, it is of practical significance to develop alow-cost separation membrane with good separation performances and easypreparation.

The selective separation membrane was prepared by self-assembly ofnanostructure materials has been a new attempt in the field ofseparation membranes in recent years. Up to now, most of thenanocomposite membranes with permselectivity have been not manufacturedin mass production for industrial application.

SUMMARY OF THE INVENTION Technical Problem

The technical problem to be solved by the present invention is toprovide a crosslinked protein-based separation membrane and applicationthereof directed to the defects of the prior art mentioned above.

Technical Solution

To solve the above technical problem, the crosslinked protein-basedseparation membrane is formed by attaching a crosslinked proteinnanomembrane to a porous membrane, the crosslinked protein nanomembraneis formed by crosslinking a two-dimensional nanomembrane which is formedby phase transition of a protein with a crosslinking agent, theseparation membrane contains a dense surface layer and a support layer,the dense surface layer is the crosslinked protein nanomembrane, and thesupport layer is the porous membrane.

The above protein is any one of lysozyme, bovine serum albumin, insulin,and α-lactalbumin. When the above protein is a lysozyme, a method offorming a lysozyme two-dimensional nanomembrane by phase transition ofthe lysozyme comprises: adjusting a pH value of a 10-100 mmol/L2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid bufferedsolution of tris(2-carboxyethyl) phosphine to 6.0-8.0 by using NaOH toget an adjusted solution; then, mixing the adjusted solution with a 1-30mg/mL 2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid bufferedsolution of the lysozyme in an isovolumetric manner to get a mixedsolution, spreading the mixed solution to a whole surface of a substratedirectly; and incubating at room temperature for 2-6 hours to, forming alayer of the lysozyme two-dimensional nanomembrane on a gas-liquidinterface of a liquid on the substrate.

When the above protein is any one of bovine serum albumin, insulin, andα-lactalbumin, a method of forming a two-dimensional nanomembrane byphase transition of the protein comprises: adjusting a pH value of a10-100 mmol/L 2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acidbuffered solution of tris(2-carboxyethyl)phosphine to 4.0-6.0 by usingNaOH to get an adjusted solution, then mixing the adjusted solution witha 1-30 mg/mL 2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acidbuffered solution of the protein in an isovolumetric manner to get amixed solution, spreading the mixed solution to a whole surface of asubstrate directly, incubating at room temperature for 2-6 hours,forming a layer of a protein two-dimensional nanomembrane on agas-liquid interface of a liquid on the substrate.

The method of crosslinking the two-dimensional nanomembrane which isformed by phase transition of the protein with the crosslinking agentcomprises: transferring the two-dimensional nanomembrane to acrosslinking agent aqueous solution with a mass fraction of 0.2%-2% forcrosslinking for 2-6 hours at room temperature; where the crosslinkingagent is any one of glutaraldehyde, Genipin, glutamine transaminase andcarbodiimide.

The above porous membrane is any one of a PET nuclear track membrane, aPC membrane, a PP membrane, a PSF membrane, and a PTFE membrane; and apore size of the porous membrane is in a range of 0.22-10 μm.

The crosslinked protein-based separation membrane of the presentinvention may serve as a dialysis membrane or an ultrafiltrationmembrane for use.

For use of the crosslinked protein-based separation membrane of thepresent invention as a dialysis membrane in the separation of mixedproteins, the mixed proteins are, for example, bovine serum albumin andinsulin, or muscle hemoglobin and insulin.

For use of the crosslinked protein-based separation membrane of thepresent invention as a dialysis membrane in the separation of mixeddyes, the mixed dyes are, for example, methyl blue and methyl orange, ormethyl blue and Rhodamine B.

For use of the crosslinked protein-based separation membrane of thepresent invention as a dialysis membrane in the removal of urotoxin byhemodialysis, the urotoxin is a toxin having a relative molecular weightless than 500, such as urea, creatinine, and a medium molecular toxinhaving a relative molecular weight in the range of 500 to 20000, such asβ-microglobulin, parathormone, leptin, renin and protein binding toxinindoxyl sulfate, and the like.

Beneficial effects of the present invention are as follows:

1. The separation membrane of the present invention is densely-piled byoligomers of a protein, colorless and transparent, and is a pure proteinmembrane. The thickness of the membrane can be controlled according tothe concentration of the protein, and the pore size decreases to 1.8 nmfrom 3.4 nm with the increase of the membrane thickness.2. The separation membrane of the present invention has goodbiocompatibility; and thus can serve as a dialysis membrane for bloodpurification to clean up urea, creatinine, and medium to large moleculartoxins, indoxyl sulfate, and the like; and moreover the separationmembrane has higher retention ratio to macromolecular proteins.Therefore, the separation membrane is a more ideal dialysis membranematerial.3. The separation membrane of the present invention can efficientlyseparate different sizes of mixed proteins and mixed dyes, such asbovine serum albumin, insulin, muscle hemoglobin and insulin, methylblue and methyl orange, methyl blue and Rhodamine B.4. The separation membrane of the present invention is easy to prepareon a large scale, has the characteristics of low cost, low energyconsumption, environmental friendliness and the like, and is free of thestep complicatedness and environmental pollution problems in traditionalsynthetic procedures of a polymer membrane.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of a scanning electron micrograph of a crosslinkedlysozyme nanomembrane in Embodiment 1.

FIG. 2 is a planar diagram of a transmission electron microscope (TEM)of the crosslinked lysozyme nanomembrane in Embodiment 1.

FIG. 3 is a diagram of an atomic force microscope (AFM) of thecrosslinked lysozyme nanomembrane in Embodiment 1.

FIG. 4 shows pore size distribution of crosslinked lysozymenanomembranes with different thicknesses.

FIG. 5 shows the removal of urea, indoxyl sulfate, creatinine andβ-microglobulin by a dialysis membrane obtained from Embodiment 1.

DETAILED DESCRIPTION OF THE INVENTION The Best Embodiment of theInvention Embodiment 1

A pH value of a 60 μL 50 mmol/L2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid bufferedsolution of tris(2-carboxyethyl) phosphine was adjusted to 7.0 by usingNaOH; and then, the adjusted solution was mixed, in an isovolumetricmanner, with a 60 μL 2 mg/mL2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid bufferedsolution of lysozyme evenly before directly spreading a resultingmixture to a whole surface of a 18 mm×18 mm cover glass; and the mixedsolution was incubated at room temperature for 2 hours to form a layerof lysozyme two-dimensional nanomembrane on a gas-liquid interface of aliquid on the cover glass; the lysozyme two-dimensional nanomembrane onthe gas-liquid interface was transferred to an glutaraldehyde aqueoussolution having a mass fraction of 1%, and then crosslinked for 2 hoursat room temperature to obtain a crosslinked lysozyme nanomembrane.

The above crosslinked lysozyme nanomembrane was attached on a PETnuclear track membrane with a diameter of 25 mm, a thickness of 12 μmand a pore size of 10 μm to obtain a dialysis membrane with thecrosslinked lysozyme nanomembrane as a dense surface layer and the PETnuclear track membrane as a support layer.

The Embodiments of the Invention Embodiment 2

In this embodiment, 2 mg/mL2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid bufferedsolution of lysozyme in Embodiment 1 was replaced with an isovolumetric4 mg/mL 2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid bufferedsolution of lysozyme; and other steps were the same as those ofEmbodiment 1 to obtain a dialysis membrane.

Embodiment 3

In this embodiment, 2 mg/mL2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid bufferedsolution of lysozyme in Embodiment 1 was replaced with an isovolumetric6 mg/mL 2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid bufferedsolution of lysozyme; and other steps were the same as those ofEmbodiment 1 to obtain a dialysis membrane.

Embodiment 4

In this embodiment, 2 mg/mL2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid bufferedsolution of lysozyme in Embodiment 1 was replaced with an isovolumetric8 mg/mL 2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid bufferedsolution of lysozyme; and other steps were the same as those ofEmbodiment 1 to obtain a dialysis membrane.

Embodiment 5

In this embodiment, 2 mg/mL2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid bufferedsolution of lysozyme in Embodiment 1 was replaced with an isovolumetric10 mg/mL 2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acidbuffered solution of lysozyme; and other steps were the same as those ofEmbodiment 1 to obtain a dialysis membrane.

Embodiment 6

In this embodiment, 2 mg/mL2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid bufferedsolution of lysozyme in Embodiment 1 was replaced with an isovolumetric20 mg/mL 2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acidbuffered solution of lysozyme; and other steps were the same as those ofEmbodiment 1 to obtain a dialysis membrane.

Embodiment 7

In this embodiment, 2 mg/mL2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid bufferedsolution of lysozyme in Embodiment 1 was replaced with an isovolumetric30 mg/mL 2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acidbuffered solution of lysozyme; and other steps were the same as those ofEmbodiment 1 to obtain a dialysis membrane.

The inventor performed SEM characterization on the crosslinked lysozymenanomembranes prepared in Embodiments 1-7; and the results showed thatthe thicknesses of the corresponding films were successively 50 nm (seeFIG. 1), 60 nm, 90 nm, 100 nm, 120 nm, 220 nm and 250 nm; and thenanomembranes were densely-piled by 20 nm oligomers after phasetransition of lysozyme (as shown in FIG. 2 and FIG. 3). The area of theprepared crosslinked lysozyme nanomembrane was controlled by a PET witha pore size of 6 mm; the membrane was made to float on 5 mL ultrapurewater; and then 50 μL 0.5 mg/mL PEG with different molecular weights wasdropwisely added on the membrane; then an UV-Vis absorption spectrum wasused to monitor the permeability of the solution standing for around 24hours, and to analyze the pore size distribution of the membrane; andthe results were shown in FIG. 4. The pore size distribution of themembrane was obtained by fitting the retention ratios of the membranefor different molecular weights; and the pore size of the membranedecreased to 1.8 nm from 3.4 nm with the increase of the membranethickness.

Embodiment 8

Use of the dialysis membrane of Embodiment 1 in the separation of methylblue and methyl orange, methyl blue and Rhodamine B, muscle hemoglobinand insulin, bovine serum albumin and insulin was specifically asfollows:

a dialysis membrane was made to float on 5 mL ultrapure water; and themembrane was separately dropwisely added with a 50 μL aqueous solutioncontaining 50 mg/L methyl blue and 50 mg/L methyl orange, a 50 μLaqueous solution containing 50 mg/L methyl blue and 50 mg/L Rhodamine, a50 μL aqueous solution containing 10 g/L muscle hemoglobin and 10 g/Linsulin, and a 50 μL aqueous solution containing 10 g/L bovine serumalbumin and 10 g/L insulin; after the solution stood for 24 hours atroom temperature, the permeability of the solution was monitored by anUV Vis absorption spectrum. The experimental results show that thedialysis membrane can completely pass through molecules having amolecular diameter of less than 2 nm; moreover, the methyl blue, bovineserum albumin and muscle hemoglobin having a molecular diameter of morethan 3 nm and carrying negative charges can be completely intercepted;the retention ratio of methyl orange is merely 0.3%, the retention ratioof Rhodamine B is 1.4%, and the retention ratio of insulin is 22.6%. Thediffusion rate of methyl orange is up to 606 nmol cm⁻² h⁻¹, and thediffusion rate of Rhodamine B is 308 nmol cm⁻² h⁻¹. Therefore, themembrane can achieve the rapid and effective separation from methyl blueand methyl orange, methyl blue and Rhodamine, muscle hemoglobin andinsulin, bovine serum albumin and insulin.

Embodiment 9

Use of the dialysis membrane of Embodiment 1 in the removal of urea,creatinine, β-microglobulin and indoxyl sulfate was specifically asfollows:

the simulation solution was an aqueous solution containing 1 mg/mLbovine serum albumin, 25 mg/L indoxyl sulfate, 40 mg/L β-microglobulin,100 mg/L creatinine and 1.5 mg/mL urea; flow velocity of the simulationsolution and dialysis fluid (water) was 10 mL/min; and dialysis wasconducted for 4 hours with a dialysis membrane. The removal ratio of thedialysis membrane for bovine serum albumin, indoxyl sulfate,β-microglobulin, creatinine and urea was tested. As shown in FIG. 5, thedialysis membrane can intercept the macromolecular bovine serum albumin;and has better removal effects for indoxyl sulfate, urea,β-microglobulin, and creatinine; and the removal ratios wererespectively 33.1%, 82.2%, 50.3% and 81.3%.

Embodiment 10

A pH value of a 60 μL 50 mmol/L2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid bufferedsolution of tris(2-carboxyethyl) phosphine was adjusted to 5.0 by usingNaOH; and then, the adjusted solution was mixed with a 60 μL 5 mg/mL2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid bufferedsolution of bovine serum albumin evenly before directly spreading aresulting mixture to a whole surface of a 18 mm×18 mm cover glass; andthe mixed solution was incubated at room temperature for 2 hours to forma layer of bovine serum albumin two-dimensional nanomembrane on agas-liquid interface of a liquid on the cover glass; the bovine serumalbumin two-dimensional nanomembrane on the gas-liquid interface wastransferred to a Genipin aqueous solution having a mass fraction of 1%,and then crosslinked for 2 hours at room temperature to obtain acrosslinked bovine serum albumin nanomembrane. The obtained crosslinkedbovine serum albumin nanomembrane was attached on a PC membrane with adiameter of 25 mm, a thickness of 12 μm and a pore size of 10 μm toobtain a dialysis membrane with the crosslinked bovine serum albuminnanomembrane as a dense surface layer and the PC membrane as a supportlayer. The use of the dialysis membrane in the removal of urea,creatinine, β-microglobulin and indoxyl sulfate was the same as that inEmbodiment 9. The experimental results show that the dialysis membranecan intercept the macromolecular bovine serum albumin; and has betterremoval effects for indoxyl sulfate, urea, β-microglobulin, andcreatinine; and the removal ratios were respectively 44.2%, 90.2%, 60.4%and 88.6%.

Embodiment 11

A pH value of a 60 μL 50 mmol/L2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid bufferedsolution of tris(2-carboxyethyl) phosphine was adjusted to 4.0 by usingNaOH; and then, the adjusted solution was mixed with a 60 μL 2 mg/mL2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid bufferedsolution of α-lactalbumin evenly before directly spreading a resultingmixture to a whole surface of a 18 mm×18 mm cover glass; and the mixedsolution was incubated at room temperature for 2 hours to form a layerof α-lactalbumin two-dimensional nanomembrane on a gas-liquid interfaceof a liquid on the cover glass; the α-lactalbumin two-dimensionalnanomembrane on the gas-liquid interface was transferred to a glutaminetransaminase aqueous solution having a mass fraction of 1%, and thencrosslinked for 2 hours at room temperature to obtain a crosslinkedα-lactalbumin nanomembrane. The obtained crosslinked α-lactalbuminnanomembrane was attached on a PP membrane with a diameter of 25 mm, athickness of 12 μm and a pore size of 10 μm to obtain a dialysismembrane with the crosslinked α-lactalbumin nanomembrane as a densesurface layer and the PP membrane as a support layer. The use of thedialysis membrane in the removal of urea, creatinine, β-microglobulinand indoxyl sulfate was the same as that in Embodiment 9. Theexperimental results show that the use of the dialysis membrane in theremoval of urea, creatinine, β-microglobulin and indoxyl sulfate was thesame as that in Embodiment 9; and the dialysis membrane can completelyintercept the macromolecular bovine serum albumin; and has betterremoval effects for indoxyl sulfate, urea, β-microglobulin, andcreatinine; and the removal ratios were respectively 35.1%, 89.2%, 51.4%and 87.5%.

Embodiment 12

A pH value of a 60 μL 50 mmol/L2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid bufferedsolution of tris(2-carboxyethyl) phosphine was adjusted to 6.0 by usingNaOH; and then, the adjusted solution was mixed with a 60 μL 2 mg/mL2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid bufferedsolution of insulin evenly before directly spreading a resulting mixtureto a whole surface of a 18 mm×18 mm cover glass; and the mixed solutionwas incubated at room temperature for 2 hours to form a layer of insulintwo-dimensional nanomembrane on a gas-liquid interface of a liquid onthe cover glass; the insulin two-dimensional nanomembrane on thegas-liquid interface was transferred to a1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride aqueoussolution having a mass fraction of 1%, and then crosslinked for 2 hoursat room temperature to obtain a crosslinked insulin nanomembrane. Theobtained crosslinked insulin nanomembrane was attached on a PSF membranewith a diameter of 25 mm, a thickness of 12 μm and a pore size of 10 μmto obtain a dialysis membrane with the crosslinked insulin nanomembraneas a dense surface layer and the PSF membrane as a support layer. Theuse of the dialysis membrane in the removal of urea, creatinine,β-microglobulin and indoxyl sulfate was the same as that in Embodiment9. The experimental results show that the use of the dialysis membranein the removal of urea, creatinine, β-microglobulin and indoxyl sulfatewas the same as that in Embodiment 9; and the dialysis membrane cancompletely intercept the macromolecular bovine serum albumin; and hasbetter removal effects for indoxyl sulfate, urea, β-microglobulin, andcreatinine; and the removal ratios were respectively 32.1%, 83.6%, 50.1%and 86.1%.

1-14. (canceled)
 15. A crosslinked lysozyme-based dialysis membrane,wherein the dialysis membrane is formed by attaching a crosslinkedlysozyme nanomembrane to a PET nuclear track membrane, the crosslinkedlysozyme nanomembrane is formed by crosslinking a two-dimensionalnanomembrane which is formed by phase transition of a lysozyme with aglutaraldehyde, the dialysis membrane contains a dense surface layer anda support layer, the dense surface layer is the crosslinked lysozymenanomembrane, and the support layer is the PET nuclear track membrane; amethod of forming a lysozyme two-dimensional nanomembrane by phasetransition of the lysozyme comprises: adjusting a pH value of a 10-100mmol/L 2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid bufferedsolution of tris(2-carboxyethyl) phosphine to 6.0-8.0 by using NaOH toget an adjusted solution, then mixing the adjusted solution with a 1-30mg/mL 2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid bufferedsolution of the lysozyme in an isovolumetric manner to get a mixedsolution, spreading the mixed solution to a whole surface of a substratedirectly, incubating at room temperature for 2-6 hours, forming a layerof the lysozyme two-dimensional nanomembrane on a gas-liquid interfaceof a liquid on the substrate; a method of crosslinking the lysozymetwo-dimensional nanomembrane which is formed by phase transition of thelysozyme with the glutaraldehyde comprises: transferring the lysozymetwo-dimensional nanomembrane to a glutaraldehyde aqueous solution with amass fraction of 0.2%-2% for crosslinking for 2-6 hours at roomtemperature.
 16. The crosslinked lysozyme-based dialysis membraneaccording to claim 15, wherein a diameter of the PET nuclear trackmembrane is 25 mm, a thickness of the PET nuclear track membrane is 12μm, a pore size of the PET nuclear track membrane is in a range of 1-10μm.
 17. Use of the crosslinked lysozyme-based dialysis membrane in theseparation of mixed proteins according to claim 15, wherein the mixedproteins are bovine serum albumin and insulin, or muscle hemoglobin andinsulin.
 18. Use of the crosslinked lysozyme-based dialysis membrane inthe separation of mixed dyes according to claim 15, wherein the mixeddyes are methyl blue and methyl orange, or methyl blue and Rhodamine B.19. Use of the crosslinked lysozyme-based dialysis membrane in theremoval of urotoxin according to claim 15, wherein the urotoxin is anyone of urea, creatinine, β-microglobulin and indoxyl sulfate.